1. Field of the Invention
This invention relates generally to cigarettes and the wrappers for the tobacco columns thereof and more particularly to an improved method for obtaining high porosity, high carbon content wrappers for cigarettes which significantly reduce particulate and vapor phase constituents of smoke obtained from the cigarette as well as reducing the amount of visible sidestream smoke that normally emanates therefrom without increasing the carbon monoxide yields obtained in the smoke when compared to cigarettes employing conventional wrappers.
2. Description of the Prior Art
Cigarettes or cigars constructed with an inner wrapper of carbon filled paper surrounding the tobacco column under an outer wrapper of conventional cigarette paper are well known as disclosed and claimed in U.S. Pat. No. 3,744,496. Such carbon filled wrappers are made using an ordinary paper furnish such as wood pulp or flax fiber to which is added a quantity of pulverized carbon as a filler. The furnish of fiber and carbon filler is then used to make paper on a conventional papermaking machine. When made into cigarettes, the combination of carbon filled paper inner wrap and conventional outer wrap results in a reduction of the tobacco weight necessary to make a satisfactory product, increases the tobacco rod firmness, and does not alter the appearance of the cigarette or cigar since the outer wrap of conventional cigarette paper or cigar wrap hides the gray carbon filled inner wrapper. More importantly, such carbon filled wrappers are extremely successful in significantly reducing organic vapor phase components and total particulate matter yields normally found in the smoke from such smoking articles and, in addition, result in a substantial reduction in the visible sidestream smoke that normally emanates from a cigarette or cigar during static burning. While these are very desirable and extremely valuable attributes of such smoking article constructions, they have one disadvantage in that the carbon monoxide yield in the smoke from such cigarette constructions tends to be substantially greater than that found in the smoke from conventional cigarettes wrapped with a single wrap of ordinary cigarette paper. Also, the manufacture of such carbon filled wrappers is messy when produced on conventional Fourdrinier papermaking machines and due to the amounts of carbon that must be used in the paper furnish to obtain a satisfactory product, it is difficult to obtain a product having sufficient tensile strength to be used on cigarette making machines, particularly when the amount of carbon is greater than 20% by weight of the paper. Furthermore, the paper itself tends to continually dust off carbon during normal handling operations.
Composite wrappers for cigarettes have also been disclosed in U.S. Pat. No. 3,395,714 in which the outer wrapper is conventional cigarette paper and the inner wrapper next to the tobacco column is a low temperature melting point heat insulating plastic sheet material. Various metal coated cigarette papers have also been suggested in the prior art as for example in U.S. Pat. No. 3,586,005, which discloses a cigarette paper wrapper in which the paper is coated on either or both surfaces with a thin layer of metal such as aluminum or aluminum based alloys. However, all of these wrappers are nonporous and essentially impervious to air. Therefore, they are unacceptable in cigarette applications where air attenuation in the tobacco column is desired.
Accordingly, it is an object of this invention to provide a method for producing high porosity, high carbon containing paper wrappers which when employed in cigarettes are effective in reducing total particulate matter yields and organic vapor phase constituents in the mainstream smoke while simultaneously reducing the visible sidestream smoke without increasing the carbon monoxide yields when compared to the smoke from conventional cigarettes constructed with ordinary cigarette paper.